The present invention relates to a solar heat collector, and more particularly to a solar heat collector for heating a heat-transfer medium such as water with the solar heat.
Solar heat collectors mounted on roofs have found wide use as an energy saver for supplying solar-heated water to bathrooms and kitchens. Such solar heat collectors have heat absorbing panels having passages through which a heat-transfer fluid flows. One type of solar heat collector is composed of a pair of heat absorbing panels pressed to jointly define therebetween a plurality of parallel passages or channels for passage therethrough of a heat-transfer fluid. According to another solar collector construction, a pair of heat absorbing panels are overlapped one on the other, and are welded together along parallel lines with a laser beam, and then a fluid under high pressure is forced in between the welded panels to deform them until panel portions between the welded seams bulge thus forming fluid passages and a header. With the solar heat collector of the latter type, localized stresses tend to be imposed on the ends of the parallel welded seams defining the fluid passages and the seam ends are liable to get cracked when the high-pressure fluid is introduced or the solar heat collector thus fabricated is in use. Therefore, such unwanted cracks render the fabrication of the solar heat collector subject to a poor yield, or the solar heat collector apt to malfunction while in use. Furthermore, the portions of the panels which define the fluid passages and header are prone to irregular plastic deformation when they are to bulge under the pressure of the introduced fluid, so that the header and adjacent areas of the fabricated solar heat collector will have uneven deformations.